Petroleum coke and certain similar granular materials are processed by passing the material in a heated state through a cooling apparatus characterized by a generally horizontally disposed rotating heat exchanger drum which is particularly configured to rotate in a water bath while the granular material is progressively passed through the interior of the drum from one end to the other to uniformly reduce the material temperature. Petroleum coke cooling apparatus, in particular, is subjected to substantial mechanical, chemical and thermal degradation of the rotary drum assembly. The granular coke material can be particularly abrasive. Moreover, gases generated by the coke together with water vapor which condenses on the drum interior can form acids particularly corrosive to steel and similar metal surfaces of the drum. Still further, thermally induced stresses accelerate the wear and tear on the drum shell and the heat exchange surfaces.
The economical production of petroleum coke requires that cooling drum assemblies be of substantial size in order to handle the volume of material to be processed. Typically, a coke cooling drum may be on the order of thirty feet in length and ten to twelve feet in diameter. A well accepted design of coke cooling drums provides for a plurality of axially and circumferentially-spaced pocket-like members formed in the drum wall which provide heat transfer surfaces for cooling the coke. At least the pockets at the inlet end of the drum are also arranged to form a somewhat helical pattern so that, upon rotation of the drum, the pockets act as auger flights to progressively move the granular coke material to minimize flooding the drum at an inlet opening disposed at one end of the drum.
The corrosive and abrasive action of the coke material together with the thermally induced stresses acting on the drum during operation can shorten the life of at least certain parts of the drum, particularly, the members forming the aforementioned cooling pockets. Accordingly, it is particularly desirable to be able to easily repair or replace the cooling pocket members without replacing a major portion of the cooling drum or without even removing the cooling drum from its working position. Moreover, there has been a continuing desire to improve the cooling efficiency and overall operating effectiveness of rotary type coke cooling drums of the type which rotate in a bath of cooling liquid, such as water. It is to these ends that the present invention has been developed.
U.S. Pat. No. 2,899,176 to Francis et al.; U.S. Pat. No. 3,917,516 to Waldmann et al.; U.S. Pat. Nos. 4,557,804; 4,667,731 to Baumgartner et al. and U.S. Pat. No. 4,747,913 to Gerstenkorn et al. (the last mentioned patent being assigned to the assignee of the present invention) describe various features of prior art coke cooling drums. The U.S. Pat. No. '176 patent to Francis et al. describes a coke cooling drum having circular segment-shaped pockets which are made up of plural welded plate members which are secured to the inside of the drum shell. The U.S. Pat. No. '516 patent to Waldmann et al. describes a coke cooling drum having generally tubular-shaped cooling pockets extending transversely therewithin and provided with abrasion or wear resistant weld metal or angle plates secured to the cooling pocket surfaces which are usually subject to severe wear. The patents to Baumgartner et al. also describe coke cooling drum water cooling pockets which are provided with wear-resistant material and the cooling pockets may be formed of a folded metal shell which may be inserted in an opening in the drum shell and welded in place. The U.S. Pat. No. '913 patent to Gerstenkorn et al. describes coke cooling drum pockets which are formed of clad plate members which are welded together to form the pocket itself. The cooling drum shell is cylindrical and has large peripheral openings for receiving the cooling pockets.
The cooling pocket members described in the prior patents identified above are not easily fabricated and are not easily inserted in and removed from the drum shell itself if it is desired to replace or repair one or more of the pockets. Moreover, the configurations of the drum shells and the cooling pockets provide for excessively large openings to be cut in the cooling drum shell which tends to weaken the drum shell thereby requiring the elongated tie rod arrangement described in the Gerstenkorn et al. patent, for example.